solid state welding processes in manufacturing

Abstract

Solid-state welding is a group of welding processes that produce sound joints at temperatures essentially below the melting point of the parent materials or without bulk melting of the parent materials. Solid-state welding processes have been widely applied in automobile, aircraft, and aerospace industries because of their enormous advantages associated with solid-state feature. The joints produced by solid-state processes are usually free of various solidification defects such as gas porosity, hot cracking, and nonmetallic inclusions, which may otherwise be present during fusion welding processes. No filler metals, flux, or shielding gas is required during solid-state welding process. The metal being joined can have mechanical properties similar to or even better than that of their parent metals due to the absence of defects and heat-affected zone in most of these processes. In addition, solid-state welding processes are also very suitable for joining dissimilar materials as their chemical compatibility, thermal expansion, and conductivity are no longer important problems. Solid-state welding, alternatively called solid-state bonding, covers a wide spectrum of processes including cold welding, forge welding, ultrasonic welding, friction welding, friction stir welding, resistance welding, diffusion bonding, and explosion welding. In these processes, bonding is achieved through deformation and diffusion at certain pressures and temperatures by using mechanical, electrical, or thermal energy. Unlike various fusion welding processes which are well known, solid-state welding is usually not well acquainted by industrial engineers. This chapter aims to give the engineers and the graduates working in relevant industries some basic knowledge in the selection of welding processes. Emphasis will be given to friction stir welding as it is a relatively new solid-state joining process and has generated great interests from various industries.